Description. Body of small size, ovate-lanceolate in form, four times as long as wide, relatively wide in front and broadest at one third of its length; moderately convex.
Cephalothorax relatively small. The carapace occupies one sixth or less of the total length of the body, is typically trapezoidal in outline, length to width as 3 : 4 or more frequently as 4 : 5; its lateral margins nearly straight, slightly converging forward, forming an obtuse, slightly rounded angle, with the nearly straight frontal margin. The posterior margin is broadly concave, the postlateral angles truncated, the truncated portion forming a distinct angle with the extremities of the concave part. The surface is moderately convex, highest in the middle near the posterior margin, where it is about one fourth as high as long. The carapace is bordered by a steeply inclined smooth marginal rim, broadest in front and narrowing toward the postlateral angles. The outer edge of the carapace is sharp; its underside is formed by the narrow doublure to which the connecting membrane is attached. The latter is frequently cleft along the anterior median line. Its width and natural position are shown in plates 5 and 6, figure 2. The compound eyes are situated a little in front of the middle, twice as far apart as distant from the lateral margin, one fifth, or less, as long as the carapace, bean-shaped, prominent, the kidneyshaped visual area entirely smooth. The two ocelli are situated on separate tubercles in a line connecting the centers of the compound eyes. Along the posterior half of the middle line a broad flat ridge (glabella) is delimited by two parallel furrows. Another pair of broader and deeper furrows passes in front and outside of the lateral eyes. These can be traced to the posterior margin, toward which they converge and become fainter. The part of the carapace outside of this furrow is very smooth. Frequently a small triangular area or a median furrow is observed on the mediofrontal part of the carapace.
The preabdomen occupies one fourth of the length of the body, and is a little wider than long. It attains its greatest width at about the fourth tergite. In the best preserved specimens it is almost evenly convex
